Re: What's the highest HP that can be squeezed from a 50cc?

Moby Dick /
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Ooh, I feel some math coming on...

Hokay, let's get HP as a function of BMEP, displacement and RPM. Easy.

HP=BMEPx(displacement/12)x(RPMx2/33000)

BMEP is in PSI and displacement is in cubic inches

If we take the crazy BMEP values some supercharged nitromethane dragsters are churning out (1450psi, which is absolutely mind boggling), and combine that with our displacement of 3.051 cubic inches, we get:

HP=1450x(3.051/12)x(RPMx2/33000)

HP=368.6625psi cu-ft x (RPM/16500)

But what shall we use for our RPM? Well, RPM as a function of mean piston speed and stroke is defined by the following:

RPM=(MPS/2xstroke)x60

I'm going to use metric for this one just to be that guy. Let's stick with a slightly less that average moped stroke length of 39mm. That will get you a slightly oversquare engine, but would not limit you overly in terms of porting. As for mean piston speed, we will again delve into the world of top fuel drag racing and F1 lunacy to pull the absolutely insane number of 30m/s out of our asses.

Note: I am aware that mean piston speed is not actually a particularly useful number for engine design. It is, however, a fuck of a lot easier to calculate than max piston acceleration which is what you actually want. It's good enough for napkin math.

RPM=(30000mm/s /2x39mm)x60

RPM=23077

If we stick that into our earlier equation, we get:

HP=368.6625psi cu-ft x (23077RPM/16500)

That leaves us with a grand total of...

515.61HP!

Disclaimer: that's a rough estimate on the back of an envelope and does not take into account air flow at all. It would be completely impossible to get anywhere near the amount of air required to do even 1/4 of that through the ports of a piston that small, even with ludicrous amounts of boost. It also doesn't take into account heat generation, which would probably require something like the cooling tower on a nuclear power plant to dissipate. It also also doesn't take into account the fact a piston or crank that would hold together at the peak acceleration generated by the piston speed we used would not be possible to construct with modern materials. I'd have to do that math, but I'd bet the acceleration would be in the ballpark of 10000g. So if you have a 100g piston, the force on the crank arm would be something like 10000N. Unless the internal bits of your engine are made of unobtanium, the sheer inertial forces would be enough to tear it apart. Finally, that number is the result of me cherry picking the highest numbers I could find from the kookiest corners of motorsports. Using these calculations, you could probably "prove" that your Civic can produce 4000HP.

But there you go, the maximum theoretical HP output of a single cylinder 50cc two stroke engine is 515. Assuming your crank and piston are made of magical pixie dust, you are running nitromethane, your engine is immersed in a bath of liquid nitrogen and there's a supercharger producing 500psi bolted to the side.

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Subject Written By Posted
  What's the highest HP that can be squeezed from a 50cc?Topic by: Jeff M Jeff M 07/24/14 11:22AM
  Re: What's the highest HP that can be squeezed from a 50cc?Re: Bob Selby Bob Selby 07/24/14 11:49AM
  Re: What's the highest HP that can be squeezed from a 50cc?Re: Jeff M Jeff M 07/24/14 11:51AM
  Re: What's the highest HP that can be squeezed from a 50cc?Re: peter heid peter heid 07/24/14 11:58AM
  Re: What's the highest HP that can be squeezed from a 50cc?Re: Jeff M Jeff M 07/24/14 12:08PM
  Re: What's the highest HP that can be squeezed from a 50cc?Re: Fred Braue Fred Braue 07/24/14 12:16PM
  Re: What's the highest HP that can be squeezed from a 50cc?Re: ashley carter ashley carter 07/24/14 12:44PM
  Re: What's the highest HP that can be squeezed from a 50cc?Re: Jeff M Jeff M 07/24/14 12:45PM
  Re: What's the highest HP that can be squeezed from a 50cc?Re: Dave & Bummerzz Dave & Bummerzz 07/24/14 01:05PM
  Re: What's the highest HP that can be squeezed from a 50cc?Re: Dave & Bummerzz Dave & Bummerzz 07/24/14 01:01PM
  Re: What's the highest HP that can be squeezed from a 50cc?Re: JOE PEG JOE PEG 07/25/14 03:02AM
  Re: What's the highest HP that can be squeezed from a 50cc?Re: ♣Slew Foot♣ ♣Slew Foot♣ 07/25/14 03:13AM
  Re: What's the highest HP that can be squeezed from a 50cc?Re: Ben -+:| Ben -+:| 07/24/14 04:31PM
  Re: What's the highest HP that can be squeezed from a 50cc?Re: Bob Selby Bob Selby 07/24/14 04:39PM
  Re: What's the highest HP that can be squeezed from a 50cc?Re: Alex Degnes Alex Degnes 07/24/14 05:01PM
  Re: What's the highest HP that can be squeezed from a 50cc?Re: Jeff M Jeff M 07/25/14 09:01AM
  Re: What's the highest HP that can be squeezed from a 50cc?Re: #CrazyWayne™ rocks. #CrazyWayne #CrazyWayne™ rocks. #CrazyWayne 07/25/14 09:23AM
  Re: What's the highest HP that can be squeezed from a 50cc?Re: Matt Mahloch -- MBM Customs Matt Mahloch -- MBM Customs 07/25/14 02:30PM
  Re: What's the highest HP that can be squeezed from a 50cc?Re: niklaus _ niklaus _ 07/25/14 06:21PM
  Re: What's the highest HP that can be squeezed from a 50cc?Re: Greg Salamander Greg Salamander 07/24/14 06:24PM
  Re: What's the highest HP that can be squeezed from a 50cc?Re: niklaus _ niklaus _ 07/24/14 06:26PM
  Re: What's the highest HP that can be squeezed from a 50cc?Re: Alex Degnes Alex Degnes 07/25/14 03:44AM
  Re: What's the highest HP that can be squeezed from a 50cc?Re: Jeff M Jeff M 07/25/14 09:03AM
  Re: What's the highest HP that can be squeezed from a 50cc?Re: niklaus _ niklaus _ 07/25/14 10:55AM
  Re: What's the highest HP that can be squeezed from a 50cc?Re: Ryan . Ryan . 07/25/14 11:20AM
  Re: What's the highest HP that can be squeezed from a 50cc?Re: SABAT! andDestroy SABAT! andDestroy 07/25/14 06:52PM
  Re: What's the highest HP that can be squeezed from a 50cc?Re: Saabsonettguy . Saabsonettguy . 07/26/14 12:44PM
  Re: What's the highest HP that can be squeezed from a 50cc?Re: ♣Slew Foot♣ ♣Slew Foot♣ 07/27/14 12:23PM
  Re: What's the highest HP that can be squeezed from a 50cc?Re: Moby Dick Moby Dick 07/28/14 12:47PM
  Re: What's the highest HP that can be squeezed from a 50cc?Re: Jeff M Jeff M 07/28/14 11:00AM
  Re: What's the highest HP that can be squeezed from a 50cc?Re: ♣Slew Foot♣ ♣Slew Foot♣ 07/28/14 10:23PM
  Re: What's the highest HP that can be squeezed from a 50cc?Re: will warn will warn 07/29/14 11:30AM
  Re: What's the highest HP that can be squeezed from a 50cc?Re: Moby Dick Moby Dick 07/29/14 03:36PM
  Re: What's the highest HP that can be squeezed from a 50cc?Re: ♣Slew Foot♣ ♣Slew Foot♣ 07/29/14 04:08PM
  Re: What's the highest HP that can be squeezed from a 50cc?Re: Moby Dick Moby Dick 07/29/14 04:50PM
  Re: What's the highest HP that can be squeezed from a 50cc?Re: will warn will warn 07/29/14 09:38PM
  Re: What's the highest HP that can be squeezed from a 50cc?Re: Moby Dick Moby Dick 07/31/14 09:41AM
  Re: What's the highest HP that can be squeezed from a 50cc?Re: ♣Slew Foot♣ ♣Slew Foot♣ 08/01/14 01:50AM
  Re: What's the highest HP that can be squeezed from a 50cc?Re: ♣Slew Foot♣ ♣Slew Foot♣ 07/30/14 02:23AM
  Re: What's the highest HP that can be squeezed from a 50cc?Re: Ryan . Ryan . 07/25/14 07:23PM
  Re: What's the highest HP that can be squeezed from a 50cc?Re: Moby Dick Moby Dick 07/25/14 09:57PM
  Re: What's the highest HP that can be squeezed from a 50cc?Re: Jeff M Jeff M 07/28/14 11:06AM
  Re: What's the highest HP that can be squeezed from a 50cc?Re: peter heid peter heid 07/25/14 10:30PM
  Re: What's the highest HP that can be squeezed from a 50cc?Re: #CrazyWayne™ rocks. #CrazyWayne #CrazyWayne™ rocks. #CrazyWayne 07/25/14 11:21PM
  Re: What's the highest HP that can be squeezed from a 50cc?Re: Jeff M Jeff M 07/28/14 12:28PM
  Re: What's the highest HP that can be squeezed from a 50cc?Re: Glenn Kuehn Glenn Kuehn 07/26/14 02:45AM
  Re: What's the highest HP that can be squeezed from a 50cc?Re: Moby Dick Moby Dick 07/26/14 10:35AM
  Re: What's the highest HP that can be squeezed from a 50cc?Re: Deadped Ryan Deadped Ryan 08/01/14 01:21PM
  Re: What's the highest HP that can be squeezed from a 50cc?Re: Moby Dick Moby Dick 08/05/14 08:21AM
  Re: What's the highest HP that can be squeezed from a 50cc?Re: ♣Slew Foot♣ ♣Slew Foot♣ 08/05/14 10:49AM
  Re: What's the highest HP that can be squeezed from a 50cc?Re: Andrew Laforest Andrew Laforest 08/05/14 04:40PM
  Re: What's the highest HP that can be squeezed from a 50cc?Re: b hat b hat 08/02/14 06:33AM
  Re: What's the highest HP that can be squeezed from a 50cc?Re: Andrew Laforest Andrew Laforest 08/03/14 10:32PM
  Re: What's the highest HP that can be squeezed from a 50cc?Re: Andrew Laforest Andrew Laforest 08/03/14 10:36PM
  Re: What's the highest HP that can be squeezed from a 50cc?Re: discontinuuity _ discontinuuity _ 08/04/14 11:39PM
  Re: What's the highest HP that can be squeezed from a 50cc?Re: ♣Slew Foot♣ ♣Slew Foot♣ 08/05/14 06:07AM
  Re: What's the highest HP that can be squeezed from a 50cc?Re: Ingvar Öhman Ingvar Öhman 03/26/22 08:25AM
  Re: What's the highest HP that can be squeezed from a 50cc?Re: ken gilbert ken gilbert 03/26/22 04:11PM

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